docs: def notFound(self):
          """Render a page with a 404 return code and a message."""
          fmt = 'The path <q>%s</q> was not understood by this server.'
          msg = fmt % (self.path,)
          openid_url = self.query.get('openid_identifier')
          self.render(msg, 'error', openid_url, status=404)